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Inbreeding Coefficient Calculator

Work out inbreeding coefficient instantly with clear inputs, formula shown and shareable results.

About Inbreeding Coefficient Calculator

Applies Wright's path coefficient method, summing one half to the power of the path length plus one over all paths through common ancestors.

Formula

Wright's formula

F = sum over paths of (0.5)^(n1 + n2 + 1) x (1 + FA), where n1 and n2 are the generations from each parent to the common ancestor

Worked example

With the default values below, Inbreeding Coefficient Calculator returns Inbreeding coefficient of 0.031250. Change any input above and every figure here is recalculated in your browser.

Inputs used

Generations from the sire to the common ancestoraccepts 1–12
2
Generations from the dam to the common ancestoraccepts 1–12
2
Independent common ancestorsaccepts 1–20
1
Inbreeding coefficient of the common ancestoraccepts 0–1
0

Results

Inbreeding coefficient
0.031250
Expressed as a percentage
3.1250%
Contribution per path
0.031250
Coefficient of relationship between the parents
0.062500

Step by step

  1. 1Values used
  2. 2Wright's formula
  3. 3Inbreeding coefficient= 0.031250
  4. 4Expressed as a percentage= 3.1250
  5. 5Contribution per path= 0.031250
  6. 6Coefficient of relationship between the parents= 0.062500

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What is F for first cousins?

0.0625, or 6.25%, from two paths through a pair of shared grandparents.

Why does it matter?

Inbreeding raises homozygosity, which increases the expression of recessive disorders and typically depresses fitness traits.

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